Quartz
Levien L, Prewitt C T, Weidner D J
American Mineralogist 65 (1980) 920-930
Structure and elastic properties of quartz at pressure
P = 61.4 kbar
_database_code_amcsd 0000794
4.702 4.702 5.256 90 90 120 *P3_221
0 0 .666666667
atom     x     y     z B(1,1) B(2,2) B(3,3) B(1,2)  B(1,3)  B(2,3)
Si   .4526     0     0 0.0084 0.0069 0.0039 0.0035 -0.0002 -0.0004
O    .4034 .2952 .0987 0.0148 0.0121 0.0064 0.0080 -0.0027 -0.0026